Cell selection and reselection for closed subscriber group cells

ABSTRACT

Apparatuses and methods are provided for performing cell reselection. A method includes camping on a non-closed subscriber group (CSG) cell that is selected using frequency priorities; scanning other frequencies for non-CSG cells and CSG cells; detecting a CSG cell being a highest ranked cell on a frequency different than a frequency of the non-CSG cell that the WTRU is camped on; and selecting the detected CSG cell, being on a whitelist, and disregarding the frequency priorities in cell selection.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/880,788, filed Oct. 12, 2015, which issued as U.S. Pat. No. 9,615,303on Apr. 4, 2017, which is a continuation of U.S. patent application Ser.No. 13/674,450, filed Nov. 12, 2012, which issued as U.S. Pat. No.9,161,298 on Oct. 13, 2015, which is a continuation of U.S. patentapplication Ser. No. 12/410,075, filed Mar. 24, 2009, which issued asU.S. Pat. No. 8,310,946 on Nov. 13, 2012, which claims the benefit ofU.S. Provisional Patent Application No. 61/038,833, filed Mar. 24, 2008,and U.S. Provisional Patent Application No. 61/082,013, filed Jul. 18,2008. All of the above-referenced applications are incorporated byreference as if fully set forth herein.

FIELD

This application is related to wireless communications.

BACKGROUND

The current effort for the 3GPP Long Term Evolution (LTE) program is tobring new technology, new architecture, and new methods in the new LTEsettings and configurations to provide improved spectral efficiency,reduced latency, and better utilization of the radio resources to bringfaster user experiences and richer applications and services with lesscost.

As part of these efforts, the 3GPP would like to introduce the conceptof a home enhanced Node B (HeNB) in LTE (and also, possibly in aparallel fashion, in Release 8 of WCDMA, GERAN, and other cellularstandards). The HeNB refers to a physical device similar to a wirelesslocal area network (WLAN) access point (AP). The HeNB provides userswith access to LTE services over extremely small service areas, such ashomes or small offices. The HeNB is intended to connect to theoperators' core network by using, for example, public Internetconnections. This can be particularly useful in areas where LTE has notbeen deployed and/or legacy 3GPP radio access technology (RAT) coveragealready exists. This may also be useful in areas where LTE coverage maybe faint or non-existent for radio transmission problems that occur, forexample, while in an underground metro or a shopping mall.

The cell (which is the term for the area over which radio coverageprovided by the HeNB is available) that is deployed by the HeNB may beaccessed only by a group of subscribers who have access to the servicesof the cell (e.g., a family) and such a cell may be referred to as aHeNB cell, or more commonly, a Closed Subscriber Group (CSG) cell. AHeNB may be used to deploy (usually) one or more CSG cells over the areawhich LTE coverage is desired. The term CSG cell may be used for a celldeployed by a HeNB for LTE services or by a HNB for WCDMA or otherlegacy 3GPP RAT services.

Cell selection and reselection criteria for CSG cells are currently anopen issue. This raises several other issues:

(1) No priority schemes exist for CSG cells.

(2) The CSG identifier that the WTRU needs to determine whether a CSGcell is configured in its white list is currently in the systeminformation blocks (SIBs). Reading the SIBs for possibly hundreds of CSGcells in a frequency layer might be unnecessarily expensive in terms oftime and power consumed.

(3) Other parameters for cell selection and reselection, such asQ_(hyst) and Q_(offset), for CSG cells are undefined.

SUMMARY

Parameters and procedures used for cell selection and cell reselectionto CSG cells are disclosed.

A method for applying a priority of a CSG cell, including receivingpriority information for each of a plurality of communicationfrequencies over which the CSG cell can communicate; storing thepriority information at a wireless transmit/receive unit; and applyingthe priority information to at least one of: taking measurements on acommunication frequency, selecting to a CSG cell in the communicationfrequency, or reselecting to a CSG cell in the communication frequency.

Methods relating to grouping CSG cells, indicating a status of a CSGcell, processing multiple CSG cells by a WTRU, reselecting between CSGcells by a WTRU, and manual CSG cell selection by a WTRU are alsodisclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding may be had from the following description,given by way of example in conjunction with the accompanying drawings,wherein:

FIG. 1 shows an example wireless communication system including aplurality of wireless transmit/receive units (WTRUs) and a home enhancedNode B (HeNB);

FIG. 2 is an example functional block diagram of one WTRU and the HeNBof FIG. 1;

FIG. 3 is a flowchart of a method for grouping CSG cells;

FIG. 4 is a flowchart of a method for processing multiple CSG cells;

FIG. 5 is a flowchart of a second method for processing multiple CSGcells;

FIG. 6 is a flowchart of a third method for processing multiple CSGcells;

FIG. 7 is a flowchart of a method for reselecting between CSG cells; and

FIG. 8 is a flowchart of a method for manual CSG cell selection.

DETAILED DESCRIPTION

When referred to hereafter, the term “wireless transmit/receive unit(WTRU)” includes, but is not limited to, a user equipment (UE), a mobilestation, a fixed or mobile subscriber unit, a pager, a cellulartelephone, a personal digital assistant (PDA), a computer, or any othertype of user device capable of operating in a wireless environment. Whenreferred to hereafter, the term “base station” includes, but is notlimited to, a Node B, a site controller, an access point (AP), or anyother type of interfacing device capable of operating in a wirelessenvironment.

FIG. 1 shows an example wireless communication system 100 including aplurality of WTRUs 110 and an HeNB 120. As shown in FIG. 1, the WTRUs110 are in communication with the HeNB 120. It is noted that, althoughan example configuration of WTRUs 110 and an HeNB 120 is depicted inFIG. 1, any combination of wireless and wired devices may be included inthe wireless communication system 100.

FIG. 2 is an example functional block diagram 200 of a WTRU 110 and theHeNB 120 of the wireless communication system 100 of FIG. 1. As shown inFIG. 2, the WTRU 110 is in communication with the HeNB 120.

In addition to the components that may be found in a typical WTRU, theWTRU 110 includes a processor 112, a transmitter 114, a receiver 116,and an antenna 118. The transmitter 114 and the receiver 116 are incommunication with the processor 112. The antenna 118 is incommunication with both the transmitter 114 and the receiver 116 tofacilitate the transmission and reception of wireless data. Theprocessor 112 of the WTRU 110 is configured to perform cell selectionand reselection.

In addition to the components that may be found in a typical HeNB, theHeNB 120 includes a processor 122, a transmitter 124, a receiver 126,and an antenna 128. The transmitter 124 and the receiver 126 are incommunication with the processor 122. The antenna 128 is incommunication with both the transmitter 124 and the receiver 126 tofacilitate the transmission and reception of wireless data. Theprocessor 122 of the HeNB 120 is configured to provide information tothe WTRU 110 usable for cell selection and reselection.

CSG Cells and the WTRU's White List

The WTRU can only access those CSG cells that are in a white list storedat the WTRU. If the WTRU attempts to access a CSG cell that is not inthe white list, the network may reject that access. Under normaloperating procedures, the WTRU first checks if a CSG cell is in itswhite list, and only if the CSG cell is in the white list should theWTRU then proceed to reselect to it.

To populate the white list, the network provides over the air signalingof the white list. The white list is written to the Universal MobileTelecommunications System (UMTS) subscriber identity module (USIM) atthe WTRU. The non-access stratum (NAS) reads the USIM and populates thewhite list in the WTRU. This is one example of an Open Mobile Affiance(OMA) protocol to populate the WTRU's white list; the specificimplementation is network-specific. Generally, the network can putWTRU-specific information on the USIM, the NAS reads the informationfrom the USIM, and the NAS further processes the information.

If the network sets a CSG cell as a public CSG cell, the WTRU does notneed to have that CSG cell in the white list. The WTRU can just accessthe CSG cell, as the network knows that it is a public CSG cell.

Priority Scheme for CSG Cells

The network signals the priority of the CSG cell frequencies to theWTRU. The WTRU can camp on the CSG cell with the highest priorityfrequency. Based on the priority of the frequencies, the WTRU will knowthe order in which it should search the frequencies. It is possible fortwo different CSG cells to be assigned the same priority. In thisinstance, the WTRU may implicitly assign a higher priority to one of theCSG cells.

In the event that all CSG cells are deployed on a single frequency (alsoknown as the CSG frequency), a macro cell (i.e., a non-CSG cell) maysignal the priority of the CSG frequency by broadcast or dedicatedsignaling. The macro cell may identify the frequency as being one forCSG cells only. There may be more than one CSG frequency.

A WTRU with no entries configured in its CSG white list can disregardthe signaled priority for the CSG frequency and will not try to initiatemeasurements, cell selection, or cell reselection to any cell on thatfrequency. If however, CSG cells are deployed on the same frequency asthe surrounding macro cells, then such a frequency may not be marked asa CSG frequency.

Alternatively, the WTRU may be pre-configured with the frequencies ofthe CSG cells it has access to and the macro cell may indicate thepriority for CSG frequencies by dedicated or broadcast signaling withoutindicating the actual frequency. WTRUs which have CSG cells andassociated frequencies configured in their white list would apply thesignaled priority to these frequencies.

Alternatively, the priority scheme for the frequency of CSG cells couldbe pre-configured in the WTRU. The configuration of the priority schemecan be sent via radio resource control (RRC)/NAS signaling or via upperlayer signaling (e.g., SMS, OMA Device configuration, etc.). In oneembodiment, the configuration of the frequencies could be done as partof the message which configures the CSG white list in the WTRU.

In addition, cell-specific priorities for CSG cells are proposed. A CSGcell configured in a white list may have a higher priority than a macrocell. Priorities of individual CSG cells versus one another may bedetermined via their broadcast signaling, by their position on the whitelist, manually entered by the user, by virtue of their group assignment(described below), or because they are determined to be public CSGcells. CSG cell priorities may be used to determine the outcome of acell reselection between CSG cells. Alternatively, when a cellreselection is considered between a CSG cell and a macro cell, the macrocell can be assumed to have the lowest priority by default, unless thepriority is specifically marked with the macro cell.

FIG. 3 is a flowchart of an exemplary method 300 for grouping CSG cellsby a WTRU. The WTRU receives priority information about each frequencyon which the WTRU can communicate (step 302) and stores the priorityinformation (step 304). The WTRU applies the priority information inconnection with taking another action (step 306), as described above.The method then terminates (step 308).

Grouping CSG Cells

CSG cells can be grouped based on the purpose for using the CSG cell,such as a home, an office, a shopping mall, etc. Each group isdistinguished by an identifier (ID). The grouping is done to easilyidentify the group type. The WTRU can determine, by reading the firstfew bits of the CSG cell identifier (for example), whether a CSG cell isa type of CSG cell that the WTRU is searching for. A WTRU subscribed toa CSG cell can only access the particular CSG cells in its white list,and cannot access other CSG cells in the same group unless those CSGcells are also in the white list.

In one implementation, the group ID is placed at the beginning of theCSG ID, so that the group ID is first and the cell ID is second. Byarranging the CSG ID in this way, a WTRU can just read the group IDportion to determine if the CSG cell may be acceptable for use.

When a WTRU detects a CSG cell, it may read its group ID to determine ifthis CSG cell has the same group ID as one that is configured in itswhite list. If the detected CSG cell has a group ID that matches thegroup ID of a CSG cell in the white list, the WTRU will continue toacquire the SIBs to verify the upper layer CSG ID (e.g., CSG TA ID).This procedure may be done as an alternative to or in addition tomatching the PCID or frequency of a detected cell with that of a CSGcell configured in the white list.

The group ID may be configured in the WTRU as part of CSG white listconfiguration. The group ID may be smaller than the CSG ID (e.g., theCSG tracking area (TA) ID). The group ID may be signaled on a physicalchannel, on the management information base (MIB), on any SIB, or on afast-changing SIB. The group ID may be certain reserved physical layercell IDs (PCIDs). Public CSG cells may be in a different group and mayhave a different group ID than private CSG cells.

Additionally, instead of preventing WTRUs from camping on certain groupsof HeNB cells, the WTRU could be given a priority order for the HeNBgroups and WTRU could try and select a cell from the HeNB group in thatorder.

The existing space for the eNB ID and cell ID in SIB1 may bere-dimensioned for CSG use. Currently, 20 bits are assigned for the eNBID and 8 bits are assigned for the cell ID. If the cell is a CSG cell(determined by using, e.g., a one bit CSG indicator on SIB1 or areserved PCID for CSG cells), then 20 bits or more may be used toidentify the HeNB and 8 bits or less are used to identify the CSG cellof that HeNB. The total number of bits used remains 28 bits or a fewmore than 28 bits (optional bits that are included only if cell is a CSGcell). The CSG ID could then be the HeNB ID plus the cell ID.

Alternatively, some bits or some indication may let the WTRU know thesize of the HeNB ID and the cell ID fields. For example, a classindication which maps to pre-defined configurations for HeNB and cell IDsizes to specific code-point values on an indicator may be used. As anexample, there could be four classes, each with different sizes of HeNBID and cell ID. Two bits on SIB1 can be used to indicate the specificclass, so that upon reading the two bits, the WTRU knows how many bitsare the HeNB ID and how many bits are the cell ID.

A separate CSG ID can be defined that identifies the specific closeduser group the CSG cell is intended to serve. This CSG ID may bedistinct from the HeNB ID and the cell ID, and may be the ID that isactually programmed in the WTRU's white list. This CSG ID may be atleast 27 bits long, may be broadcast by the CSG cell, and may be in SIB1or SIB9.

Cell Reselection Parameters for CSG Cells

A CSG cell may carry an indication (e.g., one bit) on the broadcastchannel of whether the cell is a public CSG cell or a private CSG cell.This indication may be optional or may only be used if the CSG cell ispublic or private. If this indicator is absent and the CSG indicator isset to true, the WTRU may automatically assume that the CSG cell inquestion is either public or private.

The following is a list of parameters that may be used for CSG cellreselection and indicates, for example, when to reselect to a CSG cell,when to reselect to a macro cell, and when to take measurements. Forexample, a parameter can indicate that the signal strength of the CSGcell is checked, and the WTRU can reselect to that CSG cell if it meetsthe reselection criteria and is configured in the WTRU's white list.

(1) The parameter Q_(rxlevmin) is different for CSG cells than for macroHeNB cells.

(2) A new cell selection parameter called S_(CSGsearch). IfS_(servingcell)>S_(CSGsearch), then the WTRU may not autonomously searchfor CSG cells. The WTRU may still search for CSG cells if the usermanually instructs the WTRU to do so. The parameter S_(CSGsearch) may begreater than S_(intrasearch) and/or greater than S_(intersearch). TheWTRU may apply this scheme to manual searches only, but not to anautonomous search. The parameter S_(CSGsearch) may be different forautonomous searches and manual searches.

(3) A new cell selection parameter called S_(CSGsearchneigh). IfS_(nonservingCSGcell)>S_(CSGsearchneigh), then the WTRU may measure thatnon-serving CSG cell and include it as part of the reselection process.

(4) A new parameter called Thresh_(CSG,high). If the WTRU is moving froma macro cell to a CSG cell and S_(nonservingCSGcell)>ThreSh_(CSG,high),then the WTRU may reselect to the CSG cell, provided that the CSG cellis configured in its white list or is otherwise accessible (e.g., apublic CSG cell).

(5) If the WTRU is moving from one CSG cell to another, the abovecondition (S_(nonservingCSGcell)>Thresh_(CSG,high)) may only be appliedif the neighbor CSG cell is in a higher priority frequency, a higherpriority group, or is of a higher priority (determined, for example,using its position on the white list). Alternatively, the WTRU reselectsto the higher priority CSG cell (e.g., by the white list position)regardless of the signal strength, as long as both cells' measuredsignals are above the minimum signal requirement.

(6) A new parameter called T_(CSGreselection). If the WTRU is movingfrom a macro cell to a CSG cell andS_(nonservingCSGcell)>Thresh_(CSG,high) for a time T_(CSGreselection),then the WTRU may reselect to the CSG cell provided that the CSG cell isconfigured in its white list or is otherwise accessible (e.g., a publicCSG cell).

(7) If the WTRU is moving from one CSG cell to another, the abovecondition (S_(nonservingCSGcell)>Thresh_(CSG,high) for timeTCSGreselection) may only be applied if the neighbor CSG cell is in ahigher priority frequency or a higher priority group.

(8) If the WTRU is moving from a macro cell to a CSG cell andS_(nonservingCSGcell)>0, then the WTRU may reselect to the CSG cellprovided that the CSG cell is configured in its white list or isotherwise accessible (e.g., a public CSG cell).

(9) If the WTRU is moving from one CSG cell to another and ifS_(nonservingCSGcell)>0 and S_(servingCSGcell)<S_(CSGsearch) orS_(servingCSGcell)<0, then the WTRU may reselect to the CSG cellprovided that the CSG cell is configured in its white list or isotherwise accessible (e.g., a public CSG cell).

(10) If the WTRU is moving from a macro cell to a CSG cell andS_(nonservingCSGcell)>0 for time T_(CSGreselection), then the WTRU mayreselect to the CSG cell provided that the CSG cell is configured in itswhite list or is otherwise accessible (e.g., a public CSG cell).

(11) If the WTRU is moving from one CSG cell to another and ifS_(nonservingCSGeell)>0 and S_(servingCSGcell)<S_(CSGsearch) orS_(servingCSGcell)<0 for time T_(CSGreselection), then the WTRU mayreselect to the CSG cell provided that the CSG cell is configured in itswhite list or is otherwise accessible (e.g., a public CSG cell).

(12) The parameters S_(servingcell), S_(nonservingCSGcell), andS_(servingCSGcell) are S criteria parameters and can be calculated inthe same manner as for the macro cell or by using any other equation.

(13) A new parameter called Q_(offsetCSG) may be signaled by the macrocell and applied to CSG cells for ranking them.

(14) A new parameter called Q_(hystCSG) may be signaled by the macrocell and applied to the current serving macro cell.

(15) A new parameter called Q_(hystCSGserving) may be signaled by thecurrent CSG cell and applied to the current serving CSG cell in case theWTRU is moving from one CSG cell to another or moving from a CSG cell toa macro cell.

(16) If the autonomous CSG cell search algorithm determines that a CSGcell that the WTRU has access to is nearby and should be searched for,those measurements will be made regardless of the S value of the servingmacro cell.

(17) If a CSG cell (either in the white list or manually selected) isnot the best cell on a frequency, then the WTRU may still reselect tothis cell provided at least one of the following is met.

(a) The CSG cell meets some minimum signal criteria (e.g.,S_(nonservingCSGcell)>Thresh_(CSG,high)).

(b) There is no other higher priority cell available (e.g., a higherpriority CSG cell).

(c) The serving cell (macro cell or a CSG cell) is above a certainthreshold (e.g., S_(servingcell)<S_(tolerateinterference)). Thisthreshold may be different depending on if the serving cell is a macrocell or CSG cell.

(d) The CSG cell is within a certain offset of the serving cell.

(e) The CSG cell is within a certain offset of other cells that arehigher ranking based on measurements.

(f) The CSG cell is at least a certain offset below the serving cell.

(g) The CSG cell is at least a certain offset below other cells that arehigher ranking based on measurements.

Normally, when a WTRU makes inter-frequency measurements and discoversmultiple cells which are satisfactory, it ranks the cells and camps onthe best cell. If a WTRU makes measurements on a frequency known to be aCSG frequency and detects multiple CSG cells, it will do at least one ofthe following.

(1) Disregard cells whose frequency information does not match an entryin the CSG white list or a CSG cell that is otherwise accessible (e.g.,a public CSG cell). The frequency information may be the band, centerfrequency.

(2) Disregard a cell whose PCID does not match an entry in the CSG whitelist or a CSG cell that is otherwise accessible (e.g., a public CSGcell).

(3) Disregard cells whose group ID do not match an entry in the CSGwhite list or a CSG cell that is otherwise accessible (e.g., a publicCSG cell).

(4) Rank the cells.

(5) Reselect to and camp on the best ranked cell.

FIG. 4 is a flowchart of an exemplary method 400 for processing multipleCSG cells by a WTRU. The WTRU makes measurements on a CSG frequency(step 402) and detects multiple CSG cells (step 404). The WTRU selectsone of the detected CSG cells for further evaluation (step 406).

A determination is made whether the selected CSG cell is in the WTRU'swhite list (step 408). If the selected CSG cell is in the WTRU's whitelist, then the selected CSG cell is evaluated against the cellreselection criteria (step 410). If the cell reselection criteria is met(step 412), then the WTRU reselects to the selected CSG cell (step 414)and the method terminates (step 416).

If the cell reselection criteria is not met (step 412), then adetermination is made whether all of the detected CSG cells have beenevaluated (step 420). If all of the detected CSG cells have beenevaluated, then the method terminates (step 416). If all of the detectedCSG cells have not been evaluated (step 420), then the WTRU selectsanother detected CSG cell (step 422) and this CSG cell is evaluated,beginning with step 408 as described above.

If the selected CSG cell is not in the WTRU's white list (step 408),then a determination is made whether the selected CSG cell is otherwiseaccessible (i.e., if it is a public CSG cell; step 430). If the selectedCSG cell is not otherwise accessible, the selected CSG cell is stillevaluated against the cell reselection criteria (step 410), as describedabove. If the selected CSG cell is otherwise accessible (step 430), thenthe selected CSG cell is disregarded (step 432). Next, a determinationis made whether all of the detected CSG cells have been evaluated (step420). If all of the detected CSG cells have been evaluated, then themethod terminates (step 416). If all of the detected CSG cells have notbeen evaluated (step 420), then the WTRU selects another detected CSGcell (step 422) and this CSG cell is evaluated, beginning with step 408as described above.

(6) In the event that the search was triggered by a manual searchrequest from the user, present the detected cells to the user. The WTRUmay only present those CSG cells to the user whose PCID, frequencyinformation, or group ID matches an entry in the CSG white list or a CSGcell that is otherwise accessible (e.g., a public CSG cell). Thenotification to the user may indicate that these cells have a highprobability of being the correct CSG cell to which the user has accessor a CSG cell that is otherwise accessible (e.g., a public CSG cell).The WTRU may proceed to acquire the SIBs of a particular CSG cell onlyupon receiving user input. The WTRU may prompt the user for receivingthe command to acquire the SIBs. Alternatively, all of the detected CSGcells may be presented to the user.

FIG. 5 is a flowchart of a second exemplary method 500 for processingmultiple CSG cells by a WTRU. The WTRU receives a manual search requestfrom a user (step 502). The WTRU makes measurements on the CSG frequencyindicated in the manual search request (step 504). The WTRU detectsmultiple CSG cells (step 506) and selects one of the detected CSG cellsfor further evaluation (step 508).

A determination is made whether the selected CSG cell can be accessed bythe WTRU (step 510). If the selected CSG cell can be accessed by theWTRU, then the selected CSG cell is presented to the user of the WTRU(step 512). Next, a determination is made whether all of the detectedCSG cells have been evaluated (step 514). If all of the detected CSGcells have been evaluated, then the method terminates (step 516). If allof the detected CSG cells have not been evaluated (step 514), then theWTRU selects another detected CSG cell (step 518) and this CSG cell isevaluated, beginning with step 510 as described above.

If the selected CSG cell cannot be accessed by the WTRU (step 510), thena determination is made whether all of the detected CSG cells have beenevaluated (step 514). If all of the detected CSG cells have beenevaluated, then the method terminates (step 516). If all of the detectedCSG cells have not been evaluated (step 514), then the WTRU selectsanother detected CSG cell (step 518) and this CSG cell is evaluated,beginning with step 510 as described above.

(7) Acquire the SIBs of the camped cell and verify if the upper layer ID(e.g., the CSG ID, such as the CSG TA ID) matches an entry stored in theCSG white list.

(8) If the upper layer ID (e.g., the CSG ID, such as the CSG TA ID) doesnot match an entry stored in the CSG white list or of a CSG cell that isotherwise accessible (e.g., a public CSG cell) then the WTRU realizesthat the HeNB cell was not suitable for cell reselection (e.g., the HeNBcell could be barred or belong to another operator) and the WTRU may doat least one of the following in any order.

(a) Revert to camping on the macro cell.

(b) Revert to camping on the macro cell only if macro cell was above acertain threshold.

(c) Initiate cell reselection procedures.

(d) Camp and acquire the SIBs of the next best CSG cell.

(e) Camp and acquire the SIBs of the next best CSG cell only if thereselection was initiated by a manual selection.

(f) If acquiring the SIBs or reselection was triggered by manual inputfrom user, then the WTRU may notify the user of the failure to reselectto the CSG cell. The WTRU may ask the user if he wants to initiatereselection or acquiring the SIBs of another possible candidate CSG cell(i.e., one whose PCID, group ID, or frequency information matched anentry in the white list or a CSG cell that is otherwise accessible(e.g., a public CSG cell)) or wants to revert back to a macro cell orthe last camped cell. If the user indicates that he wants to reselect tothe next possible candidate CSG cell, then the WTRU would again initiateacquiring the SIBs, etc., as described above.

FIG. 6 is a flowchart of a third exemplary method 600 for processingmultiple CSG cells by a WTRU. The WTRU makes measurements on the CSGfrequency (step 602). The WTRU detects multiple CSG cells (step 604) andselects one of the detected CSG cells for further evaluation (step 606).

A determination is made whether the ID of the selected CSG cell is inthe WTRU's white list (step 608). If the selected CSG cell is not in theWTRU's white list, then the WTRU switches away from the selected CSGcell to another detected CSG cell, using any of items (a) through (f)above (step 610).

If the ID of the selected CSG cell is in the WTRU's white list (step608), then the selected CSG cell is evaluated against the cellreselection criteria (step 612). If the cell reselection criteria ismet, then the WTRU reselects to the selected CSG cell (step 616) and themethod terminates (step 618). If the cell reselection criteria is notmet (step 614), then the WTRU selects another detected CSG cell toevaluate (step 620) and this CSG cell is evaluated, beginning with step608 as described above.

(9) If the upper layer ID (e.g., the CSG ID, such as the CSG TA ID)matches an entry stored in the CSG white list or of a CSG cell that isotherwise accessible (e.g., a public CSG cell) then the WTRU may notifythe user of the successful reselection.

The PCID of a CSG cell may be reconfigured by the user or with operatorassistance. This configuration may be, for example, based on a userdecision to reconfigure. For example, if the user feels that he has tomanually select many cells before camping on the correct one, he mightconfigure the HeNB to pick a new PCID. The HeNB could select a new PCIDfrom a reserved set of PCIDs and notify the user of the PCID orfrequency information selected (e.g., via the display). The user couldalso manually configure the PCID or frequency used by a CSG cell in itswhite list.

The manual search or selection by the user could use certain parametersfrom the autonomous search to make it more efficient. For example, ifthe user initiates a manual search and the autonomous searchconfiguration has just been completed (within some time T), or theautonomous search configuration indicates that there should not be anyCSG cell in the vicinity (e.g., using neighbor cell configurations orusing broadcast information), the user could be given an appropriatenotification and be asked to re-confirm the search parameters. Themanual search could command the WTRU to provide the user with allavailable CSG cells (e.g., even those that are not in the white list ormeet some radio related criteria). The user may be allowed to manuallyset or edit the priority of the CSG cells in the white list. Thepriority of CSG cells may be with respect to each other or with respectto macro cells, i.e., certain CSG cells may be of a lower priority thanmacro cells.

In addition, manual selection of a CSG cell may be allowed to overridethe public land mobile network (PLMN) criteria for cell selection orreselection. For example, a CSG cell that is barred because its PLMNbelongs to a forbidden PLMN may be selected by the WTRU during cellselection or reselection even if other suitable cells exist, ifcommanded to do so by the user or if the CSG ID of that CSG cell is inthe white list. Further, if a WTRU is camped on a CSG cell belonging toa particular PLMN, it may disable the search for higher priority PLMNsor background PLMN search during this time. This procedure (disablinghigher priority or background PLMN scan) may apply in at least one ofthe following cases:

(1) The WTRU is camped on a manually selected CSG cell.

(2) The WTRU is camped on a CSG cell that is in its white list.

(3) The WTRU is camped on a high priority CSG cell. The priority of theCSG cell may be indicated on the broadcast channel of the CSG cell orconfigured in the WTRU (e.g., in the white list using RRC/NAS signaling,manually entered, or through other techniques such as OMA DeviceManagement).

When a WTRU attempts to reselect to a cell that is barred by the network(meaning that the WTRU cannot camp on that cell), the network sets anintra-frequency reselection indicator to false. Setting this indicatormeans that if a cell is barred, the WTRU cannot camp on any other cellin the same frequency and needs to move to another frequency. This bitwas used in UTRAN systems and broadcast on a macro cell. If the bit wasset, then intra-frequency cell reselection was allowed. The CSG cell maynot use this indication to disallow intra-frequency cell reselection.Even if the CSG cell indicates that intra-frequency cell reselection isnot allowed, the WTRU may search for, measure, and reselect to a CSGcell on that frequency if it is in the white list or is otherwiseaccessible (e.g., a public CSG cell) and/or meets any other criteria(e.g., the radio criteria defined above). In other words, the WTRU canignore the intra-frequency reselection indicator.

Similarly, a CSG cell can set this indicator to false. But the WTRU mayoverride this setting and continue to search on the same frequency forother cells.

FIG. 7 is a flowchart of an exemplary method 700 for reselecting betweenCSG cells by a WTRU. The WTRU camps on a CSG cell (step 702) andexamines an intra-frequency reselection indicator (step 704). The WTRUcan ignore the indicator (even if set to false) and can search for CSGcells and macro cells on the same frequency (step 706). The method thenterminates (step 708).

As part of the manual selection, the WTRU access stratum (AS) may filterthe detected CSG cells which it presents to the NAS based on someradio-related criteria. As an example, it may only present those CSGcells to the NAS that are above or equal to a certain threshold.Alternatively, it may only present those CSG cells detected to the NASwhich are below a certain threshold.

FIG. 8 is a flowchart of an exemplary method 800 for manual CSG cellselection by a WTRU. The WTRU makes measurements on the CSG frequency(step 802). The WTRU detects multiple CSG cells (step 804) and filtersthe detected CSG cells based on radio-related criteria (step 806). Thefiltered cells are presented to the NAS for further evaluation (step808) and the method terminates (step 810).

Once the user manually selects a cell, the WTRU may not initiatereselection out of the cell for a predetermined period of time. Thistime may be longer than the normal T_(reselection) for which the Scriteria are evaluated. Alternatively, the WTRU may initiate reselectionright away. The WTRU may apply different reselection parameters to themanually selected CSG cell than the ones which are broadcast by the CSGcell or scale the broadcasted reselection parameters by some value.

Idle Mode Measurements and Procedures

The WTRU can use discontinuous reception (DRX) measurement gaps. If thesignal strength is greater than a threshold and the WTRU knows that itis near a CSG cell that it wants to be in, then the WTRU can overridethe DRX gaps provided by the network and use the DRX measurement gaps totake the necessary measurements. The WTRU can utilize GPS location tocheck if it is close to its home CSG cell. As the WTRU gets closer toits home CSG cell (e.g., within the footprint area), it can beginsearching for the home CSG cell. The following indicates thresholds thatthis can be based on.

The WTRU can use discontinuous reception (DRX) measurement gaps. If thesignal strength is greater than a threshold and the WTRU knows that itis near a CSG cell that it wants to be in, then the WTRU can overridethe DRX gaps provided by the network and use the DRX measurement gaps totake the necessary measurements. The WTRU can utilize GPS location tocheck if it is close to its home CSG cell. As the WTRU gets closer toits home CSG cell (e.g., within the footprint area), it can beginsearching for the home CSG cell. The following indicates that thresholdsthat this can be based on.

(1) In the Idle mode, if the WTRU is camped on a macro cell and eitherthe autonomous CSG search (e.g., using a footprint) or the manual CSGsearch is triggered that requires the WTRU to make intra-frequencymeasurements, then even if S_(servingcell)>S_(intrasearch), the WTRUwill make the measurements required and search for the CSG cell usingthe appropriate gaps (e.g., the DRX cycle idle time). If the autonomousCSG search or the manual CSG search triggered requires the WTRU to makeinter-frequency measurements, then even ifS_(servingcell)>S_(intersearch), the WTRU will make the measurementsrequired and search for the CSG cell using the appropriate gaps (e.g.,the DRX cycles).

(2) The WTRU does not make any measurements and/or search for any CSGcell.

(3) The method used may vary depending on the type of frequency. Forexample, in case of intra-frequency the WTRU searches, but in case ofinter-frequency the WTRU does not, or vice-versa.

(4) The method used may vary depending on the type of search. Forexample, in case of an autonomous search, the WTRU does not measureintra-frequency or inter-frequency if S_(servingcell)>S_(intrasearch) orS_(servingcell)>S_(intersearch), respectively. But in case of a manualsearch, if S_(servingcell)>S_(intrasearch) orS_(servingcell)>S_(intersearch), the WTRU initiates intra-frequency orinter-frequency measurements, or vice-versa.

(5) In the event that a manual search was requested by the user and forsome reason the WTRU does not perform the search (e.g., becauseS_(servingcell)>S_(intrasearch) or S_(servingcell)>S_(intersearch)), theuser may be notified of the same along with, optionally, a cause value.

The above concepts may be applicable in Active mode as well if anautonomous CSG search or a manual CSG search is triggered in Activemode, with the difference being that S_(meas) replaces S_(intrasearch)and S_(intersearch).

If the highest ranked cell is a CSG cell which is not suitable due tonot being part of the CSG white list of the WTRU, the WTRU shall treatthe cell as “barred,” as defined in section 5.3.1 of TS 36.304, exceptthat the WTRU shall consider that cell in any cell selection state asdefined in section 5.2.8 of TS 36.304.

If the highest ranked cell is a private CSG cell which is not suitabledue to not being part of the CSG white list of the WTRU, the WTRU shalltreat the cell as “barred,” as defined in section 5.3.1 of TS 36.304,except that the WTRU shall consider that cell in any cell selectionstate as defined in section 5.2.8 of TS 36.304.

Mobility-Based Speed Determination

In LTE, a count of the number of cell reselections is made to determinethe speed at which the WTRU is moving. The speed can be calculated bycounting the number of cell reselections over a given period of time.But this calculation is not accurate with CSG cells. Because the CSGcells are smaller in size, counting the number of CSG reselections couldindicate that the WTRU is moving faster than it actually is. Severalalternatives can be used to address this issue.

(1) Whenever a WTRU is camped on or in connected mode on a CSG cell, itautomatically sets its mobility state to “normal mobility.”

(2) CSG cells are not included in counting the number of cellreselections in a certain time period (e.g., T_(CRmax)) for determininga medium or high-mobility state.

(3) The WTRU is given different criteria when it counts the CSG cells todetermine its mobility state. For example, the WTRU might have to counttwo CSG cells for every macro cell it counts for its mobility criteria.

(4) The WTRU may use the number of CSG cell SIBs (e.g., a SIB from eachpassed or traversed CSG cell, reselected or not) acquired or detected aspart of an algorithm for mobility detection over CSG cells, whether inthe white list or not.

Even if the WTRU does not change its mobility state according to themobility state detection criteria for CSG cells, it might still keep atrack of the mobility changes when in a CSG cell and may retain itsmobility state detection as it moves from CSG cells to macro cells. TheWTRU may also retain its mobility state when it moves across differentfrequency layers.

Inter-cell Interference Coordination

A different power control mechanism for CSG cells than for macro cellsmay be used. The HeNB may use WTRU measurements of neighboring CSG cellsto increase or decrease the power of the CSG cell deployed by the HeNBand used by the WTRU. Different parameters for power control can be usedfor CSG cells as compared to macro cells.

The parameters, thresholds, and offsets proposed herein may beconfigured in the WTRU independently or collectively using at least oneof the following methods.

(1) Broadcast signaling on the serving cell (macro or CSG; e.g., usingSIB3).

(2) Broadcast signaling on the CSG cell that the WTRU wishes to reselectto.

(3) Dedicated signaling to the WTRU (e.g., RRC signaling or NASsignaling).

(4) As part of the CSG white list configuration in the WTRU.

(5) Pre-configured in the WTRU (and optionally stored in the USIM).

(6) A fixed value.

The parameters proposed above may be different for private CSG cells andpublic CSG cells. Some parameters may be broadcast in the macro cell aswell as in the CSG cell. As an example, the WTRU may apply some of theparameters (received from the macro cell) as it is attempting toreselect and, upon detecting the SIBs of the CSG cell, start applyingthe parameters received from the CSG cell. For example, the CSG cell maybroadcast some parameters necessary for a WTRU to reselect to it. Thisconcept may apply to macro cells as well. Some of these parameters mayinclude: S_(CSGsearch), S_(CSGsearchneigh), Thresh_(CSG,high),T_(CSGreselection), Q_(offsetCSG), Q_(hystCSG), and Q_(hystCSGserving).By setting Thresh_(CSG,high) to be a large value, a CSG cell may preventreselection to itself. This may also be used for interferencemanagement.

Although the embodiments disclosed herein relate to an LTE system, theprinciples described may also apply (with reasonable modifications) toany radio access system (e.g., WCDMA, GERAN, etc.). Although featuresand elements are described above in particular combinations, eachfeature or element can be used alone without the other features andelements or in various combinations with or without other features andelements. The methods or flow charts provided herein may be implementedin a computer program, software, or firmware incorporated in acomputer-readable storage medium for execution by a general purposecomputer or a processor. Examples of computer-readable storage mediumsinclude a read only memory (ROM), a random access memory (RAM), aregister, cache memory, semiconductor memory devices, magnetic mediasuch as internal hard disks and removable disks, magneto-optical media,and optical media such as CD-ROM disks, and digital versatile disks(DVDs).

Suitable processors include, by way of example, a general purposeprocessor, a special purpose processor, a conventional processor, adigital signal processor (DSP), a plurality of microprocessors, one ormore microprocessors in association with a DSP core, a controller, amicrocontroller, Application Specific Integrated Circuits (ASICs), FieldProgrammable Gate Arrays (FPGAs) circuits, any other type of integratedcircuit (IC), and/or a state machine.

A processor in association with software may be used to implement aradio frequency transceiver for use in a wireless transmit receive unit(WTRU), user equipment (UE), terminal, base station, radio networkcontroller (RNC), or any host computer. The WTRU may be used inconjunction with modules, implemented in hardware and/or software, suchas a camera, a video camera module, a videophone, a speakerphone, avibration device, a speaker, a microphone, a television transceiver, ahands free headset, a keyboard, a Bluetooth® module, a frequencymodulated (FM) radio unit, a liquid crystal display (LCD) display unit,an organic light-emitting diode (OLED) display unit, a digital musicplayer, a media player, a video game player module, an Internet browser,and/or any wireless local area network (WLAN) or Ultra Wide Band (UWB)module.

What is claimed is:
 1. A wireless transmit/receive unit (WTRU)comprising: a receiver and a processor configured to camp on anon-closed subscriber group (CSG) cell that is selected using frequencypriorities; the receiver and the processor are further configured toscan other frequencies for non-CSG cells and CSG cells; the receiver andthe processor are further configured to detect a CSG cell being ahighest ranked cell on a frequency different than a frequency of thenon-CSG cell that the WTRU is camped on; and the receiver and theprocessor are further configured to select the detected CSG cell, beingthe highest ranked cell on the frequency different than the frequency ofthe non-CSG cell, and disregard the frequency priorities in cellselection, wherein the detected CSG cell is on a whitelist.
 2. The WTRUof claim 1, wherein the receiver and the processor are configured toonly camp on CSG cells on a whitelist.
 3. The WTRU of claim 1, whereinthe receiver and the processor are configured to camp on a public CSGcell regardless of being on the whitelist.
 4. The WTRU of claim 1,wherein the receiver and the processor are configured to determine ahighest ranked CSG cell based on a received power level of detectedcells.
 5. A method comprising: camping, by a wireless transmit/receiveunit (WTRU), on a non-closed subscriber group (CSG) cell that isselected using frequency priorities; scanning, by the WTRU, otherfrequencies for non-CSG cells and CSG cells; detecting, by the WTRU, aCSG cell being a highest ranked cell on a frequency different than afrequency of the non-CSG cell that the WTRU is camped on; and selecting,by the WTRU, the detected CSG cell, being the highest ranked cell on thefrequency different than the frequency of the non-CSG cell, anddisregarding the frequency priorities in cell selection, wherein thedetected CSG cell is on a whitelist.
 6. The method of claim 5, whereinthe WTRU only camps on CSG cells on a whitelist.
 7. The method of claim5, wherein the WTRU camps on a public CSG cell regardless of being onthe whitelist.
 8. The method of claim 5, further comprising:determining, by the WTRU, a highest ranked CSG cell based on a receivedpower level of detected cells.
 9. A wireless transmit/receive unit(WTRU) comprising: a receiver and a processor configured to camp on aclosed subscriber group (CSG) cell, wherein the processor uses frequencypriorities in cell selection; and the receiver and the processor arefurther configured, on a condition that the WTRU is camped on the CSGcell, to treat frequencies having a higher priority than a frequency ofthe CSG cell as having a lower priority than the frequency of the CSGcell, wherein the CSG cell is on a whitelist.
 10. The WTRU of claim 9,wherein the receiver and the processor are further configured to on acondition that a camped on cell is not a CSG cell, to reselect cellsbased on the frequency priority.
 11. The WTRU of claim 9, wherein thereceiver and the processor are configured to only camp on CSG cells on awhitelist.
 12. The WTRU of claim 9, wherein the receiver and theprocessor are configured to camp on a public CSG cell regardless ofbeing on the whitelist.
 13. The WTRU of claim 9, wherein the receiverand the processor are configured to select a cell based on a receivedpower level of detected cells.
 14. A method comprising: camping, by awireless transmit/receive unit (WTRU), on a closed subscriber group(CSG) cell, wherein the WTRU uses frequency priorities in cellselection; and on a condition that the WTRU is camped on the CSG cell,treating, by the WTRU, frequencies having a higher priority than afrequency of the CSG cell as having a lower priority than the frequencyof the CSG cell, wherein the CSG cell is on a whitelist.
 15. The methodof claim 14, further comprising: on a condition that a camped on cell isnot a CSG cell, reselecting cells, by the WTRU, based on the frequencypriority.
 16. The method of claim 14, further comprising: only camping,by the WTRU, on CSG cells on a whitelist.
 17. The method of claim 14,further comprising: camping on a public CSG cell regardless of being onthe whitelist.
 18. The method of claim 14, further comprising:selecting, by the WTRU, a cell based on a received power level ofdetected cells.